Advice for a Diabetic Dog Allergic to Salmon Protein in Insulin?

I have a 7 year full breed Cairn Terrier. He has suffered with food allergies for years. I have never been able to afford allergy testing for him, but through trial and error I have been able to establish that he is allergic to all proteins in commercial dog foods. For years now he has been on Prescription Diet's Ultra Z/D. He has done well with this, with an occasional skin break out which I'm sure has to do with seasonal allergies.

Recently he was diagnosed with diabetes and is now insulin dependent, twice a day with his meals. He is now having worse allergies because unknown to me there is salmon protein in insulin. His allergies are becoming so bad that it is manifesting into ear and eye infections. Even the use of Benadryl and Atarax (antihistamines) isn't helping.

I am desperate and almost to the point of having to consider putting him down. I can't bear to do this, but my vet doesn't have any other solutions. I am also fighting for my life battling breast cancer. I love my dog and don't want to give him up. I know that Cairns have these problems and I am sure he isn't the only dog out there with this situation.

Is there anyone out there that can lend me some advise and help? I would greatly appreciate it. I'm looking into changing his diet and making it myself and using beans and rice. I'm hoping that this may help with the diabetes and maybe eliminate the need for insulin which will help with the allergies. Again, if anyone has any advise I would really appreciate it. Thank you.

By Julie from Fort Myers, FL